A diamond-like carbon (DLC) film, formed of carbon, is suitable for a wear or abrasive resistant layer of a magnetic recording medium because it has an excellent surface smoothness and a high hardness. Such a hard coating has been typically formed via a sputtering method, a plasma CVD method, or a vacuum arc evaporation method. FIG. 1 illustrates an example of an arrangement of a filtered cathodic arc (FCA) evaporation apparatus currently used in a vacuum arc evaporation method.
In the example of the arrangement in FIG. 1, a cathode material plasma P is generated at an arc source Sa. With the use of a magnetic filter 10, the plasma P is guided as a cathode material plasma beam Pb to a substrate 13, which is held in a deposition vacuum chamber 14 having a shutter 19. The magnetic filter 10 has a stainless steel pipe 11 bent in a quarter circular-arc-shape as a core, on which an electromagnet coil 12 is provided. Between the magnetic filter 10 and the deposition vacuum chamber 14, a raster coil 18 is provided. With this arrangement, a film of cathode material ions can be formed on the substrate 13. When carbon (graphite) is used as the cathode material or target in the vacuum arc evaporation apparatus, the formed film has a tetrahedral amorphous carbon (ta-C) structure, containing no hydrogen, but rich in sp3 bond carbon, with a high hardness.
At the arc source Sa in the above arrangement, with the deposition material taken as a cathode target 16, a vacuum arc discharge is induced between the cathode target 16 and an anode 17 by contacting a striker 15 with the surface of the cathode target 16 to thereby generate the cathode material plasma P. However, with this arrangement, it is difficult to stably maintain the arc discharge. Moreover, another problem is that a cathode spot of the discharge circumvents the cathode target 16, making it difficult to discharge the cathode material plasma beam Pb toward the desired direction.
Examples of an arrangement of the arc source Sa are disclosed in JP-A-2002-32907 and JP-A-2002-88466. To stably maintain arc discharge in the above arrangements, specialized arrangement of the arc source and the method of generating the arc discharge must be considered. Furthermore, in the arrangement disclosed in the latter reference, it is difficult to provide a cooling mechanism for the magnetic material.
Accordingly, there is a need for a vacuum arc evaporation apparatus or method provided with a vacuum arc discharge unit that can stably maintain vacuum arc discharge at an arc source. The present invention addresses this need.